Mosquitoes Remember Who Swats and Who Smells Good

Researchers say dopamine levels in mosquitoes’ brains teaches them what to avoid and where to return.

Mosquitoes don’t get a lot of love. No one ever talks about how cute they are.

But in the lab, the little buggers can be the star of the show.

A study published last month in the journal Current Biology shows that mosquitoes have the ability to learn and remember what their hosts smell like.

Remember thinking they were out to get you? You weren’t wrong.

Scientists at Virginia Tech concluded that even if the neighborhood mosquitoes believe you’re a walking honey hole of deliciousness, something negative — swatting, perhaps, or an electric charge — can persuade the little creatures to go elsewhere.

Clément Vinauger, an assistant professor of biochemistry in the College of Agriculture and Life Sciences, and Chloé Lahondère, a research assistant professor in the department of biochemistry, used cutting edge technology, including CRISPR gene editing and RNAi.

By using a multidisciplinary approach, the scientists told Healthline they were able to identify that dopamine is a key mediator of aversive learning in mosquitoes.

Dopamine, which is also found in humans, is a neurotransmitter that helps control the reward and pleasure centers of the brain.

It also helps regulate movement and emotional responses. It enables us not only to see rewards, but move toward them.

Twenty-four hours after the shock was applied, the same mosquitoes were assessed in a Y-maze olfactometer, in which they had to fly upwind and choose between the once-preferred human body odor and a control odor.

The mosquitoes avoided the human body odor, suggesting they had been successfully trained.

According to Vinauger, mosquitoes are the deadliest member of the animal kingdom, causing more deaths per year than any other creature.

“It’s more than [the number of] people killing each other,” he said.

Among the deadly diseases they carry are dengue fever, chikungunya, yellow fever, and the Zika virus. They can be found in tropical and subtropical regions throughout the world.

“We know they use smell to identify birds and humans to find their hosts. Women smell different than men, and beer drinkers get bitten more,” Vinauger said. “Now we can exploit this ability.”

For example, using mosquito netting around a bed will discourage the bugs from returning for another attack.

And if there’s an electric shock administered from touching the netting, this will be a greater deterrent.

“If we provide them with an alternate host, such as a rabbit, we can divert them,” Vinauger said.

Not so nice for the bunnies perhaps, but good for people.

“For the first time we started to understand this, that learning is implicated in mosquito behavior,” Lahondère said.

“We studied them by putting mosquitoes in a box and then shocked them,” she said.

Lahondère compared the technique to that of Pavlov, “except we used shocks instead of food.”

Mosquito brain

The researchers actually fitted mosquitoes with helmets that allowed for brain activity recordings and observations.

Specific parts of the brain involved in olfactory integration were highlighted.

By placing mosquitoes in an insect flight simulator and exposing them to various smells, including human body odors, the scientists observed how the insects, trained or not, reacted.

They discovered that the neural activity in the brain region where olfactory information is processed was modulated by dopamine in such a way that odors were easier to discriminate, and potentially learn, by the mosquitoes.

“Unfortunately, there is no way of knowing exactly what attracts a mosquito to a particular human. Individuals are made up of unique molecular cocktails that include combinations of more than 400 chemicals,” Lahondère told Virginia Tech News. “However, we now know that mosquitoes are able to learn odors emitted by their host and avoid those that were more defensive.”

“Understanding these mechanisms of mosquito learning and preferences may provide new tools for mosquito control,” Vinauger told Virginia Tech News. “For example, we could target mosquitoes’ ability to learn and either impair it or exploit it to our advantage.”

They tested with different types of body odor and found the mosquitoes reacted more strongly to those associated with a shock.

“There’s a lot of research and a lot of government involvement in Europe and the U.S. working on this,” Vinauger added.

Indeed, the New York Post reported that thousands of bacteria-infected mosquitoes will be flying near Miami to test a new way to suppress insect populations that carry viruses.

MosquitoMate, the Kentucky-based company that collaborated in the study, said the first batch will be released in the city of South Miami.

The test is in collaboration with the Miami-Dade County Mosquito Control and Habitat Management Division.